= Low-energy effective action
A low-energy effective action retains the light degrees of freedom and describes the effects of heavier ones through local interactions and a <derivative expansion>. It can be obtained by matching an <effective field theory> or by a low-energy <compactification>. A <Wilsonian effective action> implements integration of high-energy modes with a scale cutoff. The <quantum effective action> that generates <one-particle-irreducible vertices> is a different construction; the two need not coincide.
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